One of the words used in this period for the broad category in society a person belonged to. Today we use 'class'. Other words of the time were *degree and condition. These were considered to be clear and defined, as were the various monastic orders. Although movement upwards was very difficult, nigh impossible for the ordinary *villein, there was enough flexibility for wealthy merchants to become ennobled, e.g. the de la Poles of Hull in the 14c.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.